The present invention relates to apparatus for transporting strips, webs, tapes, bands or like flexible materials, especially for transporting webs of photosensitive material in and from the housing of a copying machine such as a photographic roll copier. More particularly, the invention relates to improvements in apparatus for transporting webs of freshly exposed photosensitive material from a copying machine into a cassette or another suitable receptacle which is held in a predetermined position with reference to the copying machine.
It is already known to equip a copying machine with an apparatus which can supply a web of photosensitive material into a cassette so that the leader of the web can be at attached to the rotary core of the cassette to be thereupon convoluted around the core in order to form a reel of desired diameter. The apparatus comprises a first advancing unit which is installed in the housing of the copying machine to transport the web from the copying machine toward the core of a cassette, and a second advancing unit which rotates the core to thus ensure that the core can wind the web therearound. Reference may be had to German Offenlegungsschrift No. 26 17 233 which discloses a copying machine with two advancing rolls serving to move the web of photosensitive material lengthwise toward and through an opening in the housing of the copying machine and thereupon through an opening of the casing forming part of a properly positioned cassette so that the leader of the web can reach the core in the interior of the cassette. The core of the properly positioned cassette is driven by the motor which transmits torque to the advancing rolls. The cassette contains a so-called catcher mechanism which steers the leader of the web toward and into engagement with the core so that the leader is convoluted around the core and its innermost convolution engages the peripheral surface of the core with a force which suffices to ensure that the core can draw the web from the interior of the copying machine. At such time, the catcher mechanism should be deactivated in order to avoid interference with accumulation of windings on the core.
As a rule, the leader of the web is advanced into the interior of an empty cassette while the copying machine is operated at the lower or lowest of two or more different speeds. The speed of the copying machine is, should or can be increased as soon as the leader is adequately attached to the core of the cassette.
A drawback of heretofore known apparatus is that proper attachment of the leader of a web to the core of the cassette cannot be recognized or detected with a requisite degree of reliability. For example, the aforementioned Offenlegungsschrift proposes to employ a mechanical detector which is supposed to monitor the progress of engagement between the leader of the web and the core of the cassette and to initiate a deactivation of the catcher mechanism when the attachment is completed. It has been found that the mechanical detector of the aforediscussed prior publication is not only unreliable but also bulky and highly prone to malfunction. Such mechanical detector is incapable of unequivocally ascertaining the exact moment when the web is adequately attached to the core so that the latter can draw the web from the housing of the copying machine. Therefore, the catcher mechanism is likely to be deactivated too soon or too late. If the deactivation is premature, the entire threading operation must be repeated or the leader must be attached to the core by hand. If the deactivation is unduly delayed, parts of the catcher mechanism are likely to damage the web.